Epidemiological study conducted in the entire Kii Peninsula revealed a unique pattern in deaths due to motor neuron disease. A review of death certificates for a ten year period gave an average annual mortality rate of 0.3-0.8 per 100,000 population in the northern part and a rate of 1.0-3.0 in the southern part. Analysis of environmental samples revealed a low calcium content in rice and well and river water used for drinking purposes in the foci areas in the southern part of the Peninsula. Based on these results, further study will be directed towards other focus areas which may be found in the Kii Peninsula and elsewhere in Japan. Analytical study using neutron activation method confirmed a significant high content of calcium in CNS of ALS cases as compared with their controls. The correlation of calcium to other divalent cations in terms of interaction in the process of soft tissue calcification within the CNS in cases of ALS will be investigated.